Conventional vacuum boosted brake apply systems utilize a direct application of pedal-to-brake force via hydraulic fluid. Drivers have become accustomed to the pedal response or “feel” generated by such systems. With brake-by-wire (BBW) or similar type of vehicle braking system, however, the application of braking force to the wheel brakes is generated by an electric or an electro-hydraulic controlled means. This changes the BBW pedal feel characteristics at the vehicle's brake pedal from those conventional apply systems and prevents the driver from experiencing the customary brake pedal feel. Therefore, strategies have been developed for emulating pedal feel that drivers are accustomed.
Known BBW systems that generate a pedal feel consistent with that of conventional vacuum boosted apply systems may utilize a master cylinder assembly to emulate pedal feel. The brake pedal feel is typically transparent to the driver when compared to the conventional vacuum boosted apply systems. Examples of such emulators include U.S. Pat. Nos. 5,729,979 and 6,367,886 to Shaw. Such brake pedal emulators may include (sequentially compressible) springs or other biasing members and restrictive fluid flow paths to generate non-linear reaction force versus pedal travel (e.g., movement of the pedal) consistent with conventional apply systems. These emulator elements are typically carried within the master cylinder assembly.
Although such assemblies may provide adequate brake pedal travel and feel characteristics, use of a master cylinder including emulator elements adds to the cost and size of the brake pedal assembly. As such, it would be desirable to provide a non-linear reaction force to pedal travel assembly and method that do not require a master cylinder or like mechanisms to generate pedal feel consistent with vacuum boosted brake apply systems.
Unlike the non-linear reaction force versus travel output of brake pedals, the accelerator, clutch, and emergency brake pedals typically exhibit a linear response that is much simpler mechanically to provide. Nevertheless, the use of spring(s) or like biasing elements to generate the pedal feel may add to the cost of the pedal assembly. As such, it would be desirable to provide a linear reaction force to pedal travel assembly and method without the need for external springs or like elements to generate the desired pedal feel.
Therefore, it would be desirable to provide a pedal feel emulator assembly and method that overcomes the aforementioned and other disadvantages.